(1) Field of the Invention
This invention relates to a hydraulic drive device for a construction machine which stops an engine when a predetermined state of the construction machine has continued for a predetermined period of time.
(2) Description of the Related Art
As a hydraulic drive device of this type, a hydraulic drive device has been devised which includes a gate lock lever (gate bar) provided near the side of the operator's seat of the construction machine, and an engine stopping unit that stops the engine in accordance with the position of this gate lock lever. The gate lock lever is operated to switch between a close position in which the gate lock lever projects obliquely toward the boarding entrance to close the boarding entrance, and an open position in which the gate lock lever retracts toward the side of the operator's seat to open the boarding entrance. This gate lock lever is provided with a position detecting unit that outputs a gate close signal upon detecting that the gate lock lever is in the close position, and outputs a gate open signal upon detecting that the gate lock lever is in the open position. The engine stopping unit is set to stop the engine when a predetermined period of time has elapsed in the state in which the gate open signal is outputted from the position detecting unit, in other words, in the state in which the gate lock lever is in the open position. The gate lock lever is operated to switch from the close position to the open position when the operator of the construction machine leaves the cabin. That is, the engine stops when a predetermined period of time has elapsed after the operator of the construction machine leaves the cabin without stopping the engine. This can contribute to reducing wasted fuel consumption, and also reducing environmental destruction such as global warming due to exhaust gas (see Japanese Patent No. 3811169).
Also, as another hydraulic drive device according to the related art different from the hydraulic drive device described above, there is a hydraulic drive device which includes an exhaust emission control device. This exhaust emission control device has an exhaust filter provided to the exhaust pipe of the engine, and captures particulate matter contained in exhaust gas by this exhaust filter. When this exhaust filter becomes clogged with particulate matter, the hydraulic drive device performs regeneration control for removing the particulate matter from the exhaust filter by burning the particulate matter, in other words, for regenerating the function of the exhaust filter. This regeneration control is, for example, a control for raising the discharge pressure and discharge flow rate of a variable displacement hydraulic pump driven by the engine, thereby increasing the load applied to the engine to raise the temperature of exhaust gas to a sufficient temperature for the particulate matter to burn (see Japanese Patent No. 3073380).